Fig. 1 Experimental setup. The capacitor structure consists of the Pt/Co/Pd asymmetric layers, 50-nm HfO2 gate insulator, and Cr/Au electrode. A pulsed perpendicular magnetic field Hz was applied to drive the DW. The Hz was generated using a 500-μm-diameter coil placed on the sample. The DW motion was observed using a MOKE microscope. The typical MOKE image obtained by subtracting two MOKE images taken before and after the application of the pulsed Hz is shown. The DW velocity v was calculated from the DW displacement L by the Hz application.
Fig. 2 Perpendicular magnetic field dependence of DW velocity. v as a function of Hz obtained under the gate voltage VG of 0 V (circle), +15 V (square), and −15 V (triangle) for the samples with Co thickness tCo = (A) 0.78 nm and (B) 0.98 nm is shown. The error bar is the SD of five measurements for each μ0Hz. The insets show VG dependence of the saturation v (vs) in a high Hz regime. The error bar is the SD of vs.
Fig. 3 Gate voltage dependence of the areal iDMI and PMA. VG dependence of the areal iDMI magnitude Dt for the sample with tCo = (A) 0.78 nm and (B) 0.98 nm is shown. Dt is determined using the vs and areal magnetic moment of the sample following Eq. 1. a.u., arbitrary units. The error bar indicates the error of vs. Areal PMA energy Kut as a function of VG for the tCo = (C) 0.78 nm and (D) 0.98 nm samples is shown.
Fig. 4 In-plane field dependence of the DW velocity under gate voltage. (A) v as a function of static in-plane magnetic field Hx for the sample with 0.98-nm Co thickness. The negatively polarized (N domain) and positively polarized (P domain) domain expansion cases are displayed. μ0Hz of 178 mT was applied to drive the DW. The MOKE image is the subtracted image obtained under μ0Hx = +72 mT for N domain case. (B) v measured under an in-plane static field Hx at VG = +15 V (circle) and −15 V (triangle) for the sample with tCo = 0.98 nm. |μ0Hz| of 100 mT was applied to drive the DW. The dashed lines indicate the DMI effective fields HD for VG = +15 and −15 V. The error bar is the SD of 10 measurements for each μ0Hx.
Supplementary Materials
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/12/eaav0265/DC1
Section S1. EF effect on areal magnetic moment and anisotropy energy
Section S2. Numerical calculation of the saturation DW velocity
Fig. S1. Schematic illustration of the capacitor structure for the areal magnetization measurement.
Fig. S2. In-plane magnetization curves for the studied samples.
Fig. S3. Simulated DW velocities as a function of external magnetic field and the anisotropy and DMI dependences of the DW velocity.
Table S1. Summary of the capacitances for the capacitors.
Reference (31)
Additional Files
Supplementary Materials
This PDF file includes:
- Section S1. EF effect on areal magnetic moment and anisotropy energy
- Section S2. Numerical calculation of the saturation DW velocity
- Fig. S1. Schematic illustration of the capacitor structure for the areal magnetization measurement.
- Fig. S2. In-plane magnetization curves for the studied samples.
- Fig. S3. Simulated DW velocities as a function of external magnetic field and the anisotropy and DMI dependences of the DW velocity.
- Table S1. Summary of the capacitances for the capacitors.
- Reference (31)
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